From fa0b8668fb49f1577f5bea990b04a95e1b9d9124 Mon Sep 17 00:00:00 2001
From: Cedric Roux <cedric.roux@eurecom.fr>
Date: Mon, 27 Mar 2017 16:27:56 +0200
Subject: [PATCH] bugfix: workaround a problem with timestamp and LMSSDR.
We have a strange problem with the timestamp of the very
first packets received from the LimeSDR that leads to
a complete failure of the eNB.
A simple workaround is to discard the first RX packet
just after a "start" of the device.
We also change the value of "tx_sample_advance" to a more
reasonable value. The problem of timestamp was "solved"
differently in the past and at the time we needed to put
a much higher value.
This may have to be refined at some point.
---
targets/ARCH/LMSSDR/USERSPACE/LIB/lms_lib.cpp | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/targets/ARCH/LMSSDR/USERSPACE/LIB/lms_lib.cpp b/targets/ARCH/LMSSDR/USERSPACE/LIB/lms_lib.cpp
index f2d2af55c7..2dec4ff22d 100644
--- a/targets/ARCH/LMSSDR/USERSPACE/LIB/lms_lib.cpp
+++ b/targets/ARCH/LMSSDR/USERSPACE/LIB/lms_lib.cpp
@@ -45,6 +45,14 @@ lms_device_t* lms_device;
lms_stream_t rx_stream;
lms_stream_t tx_stream;
+/* We have a strange behavior when we just start reading
+ * from the device (inconsistent values of the timestamp).
+ * A quick solution is to discard the very first read packet
+ * after a "start".
+ * The following global variable "first_rx" serves that purpose.
+ */
+static int first_rx = 0;
+
#define RXDCLENGTH 4096
#define NUMBUFF 32
@@ -94,6 +102,10 @@ int trx_lms_read(openair0_device *device, openair0_timestamp *ptimestamp, void *
meta.flushPartialPacket = false;
int ret;
+ if (first_rx == 1) {
+ first_rx = 0;
+ ret = LMS_RecvStream(&rx_stream,buff[0],nsamps,&meta,50);
+ }
ret = LMS_RecvStream(&rx_stream,buff[0],nsamps,&meta,50);
*ptimestamp = meta.timestamp;
return ret;
@@ -223,6 +235,8 @@ int trx_lms_start(openair0_device *device){
}
+ first_rx = 1;
+
rx_stream.channel = 0;
rx_stream.fifoSize = 256*1024;
rx_stream.throughputVsLatency = 0.1;
@@ -355,7 +369,7 @@ int device_init(openair0_device *device, openair0_config_t *openair0_cfg){
break;
case 15360000:
openair0_cfg[0].samples_per_packet = 2048;
- openair0_cfg[0].tx_sample_advance = 450;
+ openair0_cfg[0].tx_sample_advance = 50; /* TODO: to be refined */
openair0_cfg[0].tx_bw = 15.36e6;
openair0_cfg[0].rx_bw = 15.36e6;
break;
--
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